Oooh I actually know what the mucus problem is. You might want to invest in Tylan powder for the future and do some research on Chicken MG
here is a link
http://edis.ifas.ufl.edu/ps034
Its really common in chcikens, mine got it a while back, but it was beyond the point that I could control it. I strongly suggest you take steps now for your little fluffy babys :D